1. Field of the Invention
The present invention relates to a surface texture measuring apparatus, and more particularly to such an apparatus capable of coping with vibration during measurement.
2. Description of the Related Art
Surface texture measuring apparatuses are commonly known that scan a surface of a measured object (workpiece) with a detector having a stylus to measure unevenness (or roughness) of the surface.
In such a surface texture measuring apparatus, the stylus is moved in a fixed direction (direction of the X axis), and displacement of the stylus in the vertical direction (direction of the Z axis) caused by unevenness of the workpiece is converted to electric signals, which are sampled by a scale signal or a fixed time signal, so that the unevenness (roughness, winding, shape, or the like) is analyzed as a function of the traveled distance (in the X axis direction) and displayed on a display device or printed by a printing device.
In surface texture measurement of a workpiece, unevenness smaller than a few xcexcm is generally detected, and therefore even a very minute vibration adversely affects measurement data as disturbance.
Although a workpiece may be placed on a vibration-proof table to avoid such vibration, this is not always effective enough for measurement of a very small unevenness, and therefore reliability of measurement data becomes a problem. More specifically, vibration disturbance is caused by a person walking in a measurement room, and has adverse effects on data obtained during highly sensitive measurement even if the vibration-proof table is used, and therefore considerable care must be exercised, even when walking.
In addition, deformation caused by a worn-out reduction gear or a motor contained in the measurement apparatus itself may be a vibration source.
An object of the present invention is to provide a measuring apparatus that allows surface texture of a workpiece to be measured with a high accuracy even when vibration disturbance is generated during measurement.
In order to achieve the above object, the measuring apparatus of the present invention relates to a surface texture measuring apparatus for moving a stylus in a first axis direction along a workpiece to detect displacement of the stylus in a second axis direction perpendicular to the first axis direction resulting from surface texture of the workpiece, including detection means for detecting vibration of the workpiece, and output means for outputting the detected vibration in association with the movement of the stylus in the first axis direction. By detecting vibration of the workpiece, correction can be made to remove vibration components included in the displacement of the stylus in the second axis direction. The correction for removing the vibration can be made by the surface texture measuring apparatus. Alternatively, the surface texture measuring apparatus may output measurement data, i.e. displacement data accompanied with the movement in the first direction and vibration data, to an external device, which eliminates vibration components.
The detection means for detecting vibration preferably includes a second stylus, and means for bringing the second stylus into contact with the surface of the workpiece to detect displacement of the second stylus in the second axis direction at a contact position. A second surface texture measuring apparatus having the second stylus can be used for such a detecting unit.
More specifically, although the second surface texture measuring apparatus has a function of common surface texture measuring apparatuses, namely, a function of moving the second stylus along the workpiece and detecting displacement of the stylus in the second axis direction resulting from surface texture of the workpiece, the second surface texture measuring apparatus of the present invention does not move the second stylus along the workpiece, but detects the displacement of the second stylus in the second axis direction as the vibration.
Preferably, the detection means for detecting vibration includes means for outputting a signal synchronized with a timing for detecting the displacement of the stylus in the second axis direction accompanied with movement in the first axis direction. By using the signal synchronized with the timing for detecting surface texture of the workpiece as a sampling signal to detect the vibration, vibration can be detected in synchronization with measurement of the surface texture of the workpiece.
When the second surface texture measuring apparatus is used as the detection means for detecting vibration, the second surface texture measuring apparatus preferably includes means for receiving a signal synchronized with a timing for detecting displacement of the stylus in the second axis direction, and means for detecting the vibration by using the synchronized signal as a sampling signal. Thus, vibration can be detected in synchronization with measurement of the surface texture of the workpiece.
A surface texture measuring apparatus of the present invention includes means for stopping the stylus at the surface of the workpiece, means for detecting displacement of the stylus in the second direction in a stopped state as vibration of the workpiece, and means for outputting the vibration and displacement in a moving state. No separate vibration sensor is provided to the surface texture measuring apparatus, but instead the surface texture measuring apparatus itself serves as a vibration sensor. More specifically, the stylus is stopped at the surface of the workpiece without moving in the first axis direction, and displacement in the second axis direction is detected in the stopped state. This displacement is caused by vibration of the workpiece, not by the surface texture thereof. Considering that this vibration is also generated in the state where the stylus is moving at the workpiece surface in the first axis direction, vibration components can be removed from the measurement data of the surface texture of the workpiece.
A surface texture measuring apparatus of the present invention includes means for switching states where the stylus is moving in the first axis direction and is stopped, means for detecting displacement of the stylus in the second axis direction in the state where the stylus is stopped, means for detecting displacement of the stylus in the second axis direction in the state where the stylus is moving, and means for outputting the above two displacements. Surface texture measurement and vibration measurement are alternately conducted by switching the moving state and the stopped state. Consequently, the amount of vibration at the time surface texture of the workpiece is being measured can be detected with a high accuracy.